Process for producing diacetoxybutene

ABSTRACT

In yielding diacetoxybutene by feeding butadiene, acetic acid, and oxygen in the presence of a solid catalyst containing palladium, the butadiene can be efficiently reacted to produce diacetoxybutene in high yield by feeding an oxygen-containing gas containing 7 mol % or more oxygen as fine bubbles to a reaction zone containing the solid catalyst.

TECHNICAL FIELD

The present invention relates to a process for producing diacetoxybuteneby reacting butadiene, acetic acid, and oxygen, and to others.Diacetoxybutene is an important compound as an intermediate forproducing 1,4-butanediol or tetrahydrofuran.

BACKGROUND ART

The technique of reacting butadiene, acetic acid, and oxygen in thepresence of a solid catalyst containing palladium to yielddiacetoxybutene is known. Since the reaction proceeds in a liquid phase,it is important for efficiently carrying out the reaction to accelerateoxygen transfer from the gaseous phase to the liquid phase and therebymaintain a high oxygen concentration in the liquid phase.

Diacetoxybutene has hitherto been produced by a method of reaction inwhich a catalyst is disposed as a fixed bed in an oxygen-containingatmosphere and a liquid comprising butadiene and acetic acid is causedto flow down along the surface of the catalyst (see, for example,Japanese Patent Publication No. 42057/1980). This method of reaction,however, has the danger of generating an explosive mixed gas because thebutadiene and acetic acid, which are liquid feed materials, partlyvaporize and come into the oxygen-containing atmosphere, which is acontinuous phase. Consequently, it has been necessary to regulate theoxygen concentration in the atmosphere so as to be lower than the lowerexplosion limit. It is a matter of course that low oxygen concentrationsin the atmosphere constitute an obstacle to the acceleration of oxygendissolution in the liquid.

In Japanese Patent Laid-Open No. 129514/1975 is disclosed a process forcontinuously producing diacetoxybutene which comprises feedingbutadiene, acetic acid, and oxygen as upward cocurrent flows to areactor in the presence of a fixed-bed catalyst comprising a supportedpalladium catalyst. However, this process, in which a gas containingoxygen is supplied to the liquid feed-materials constituting acontinuous phase, has the following drawbacks. The gas forms largebubbles and these bubbles are apt to coalesce with one another. Becauseof this, the area of the gas/liquid interface is apt to become small.Since the dissolution of oxygen in the feed liquid which is being fed tothe fixed-bed catalyst is hence insufficient, the oxygen concentrationin the liquid is insufficient, resulting in a reduced reactionefficiency. Furthermore, there is the danger of generating an explosivemixed gas because butadiene and acetic acid, which are liquid feedmaterials, partly vaporize and come into the bubbles. Consequently, asin the case of the method of reaction described above in which feedmaterials are caused to flow down, the oxygen concentration in thebubbles should be kept lower than the lower explosion limit and this isan obstacle to the acceleration of oxygen dissolution in the liquid.

A subject for the invention is to provide a method for efficientlyreacting butadiene to produce diacetoxybutene in high yield, and toprovide others.

DISCLOSURE OF THE INVENTION

The present inventors made intensive investigations in order toaccomplish the subject described above. As a result, it has been foundthat when butadiene, acetic acid, and oxygen are fed to a reaction zonein which a solid catalyst containing palladium is present, the butadienecan be efficiently reacted and diacetoxybutene can be produced in highyield by introducing an oxygen-containing gas containing 7 mol % or moreoxygen into a liquid phase comprising acetic acid and butadiene in sucha manner that the gas forms fine bubbles.

It has also been found that by disposing, under the catalyst-packed bed,flow control plates projecting downward from the lower side of the bed,butadiene can be efficiently reacted and diacetoxybutene can be producedin high yield.

Furthermore, it has been found that regulating the catalyst-packed bedso as to have a porosity of from 0.30 to 0.41 is effective inefficiently reacting butadiene and producing diacetoxybutene in highyield.

The invention has been completed based on those findings.

Namely, the first essential point of the invention resides in a processfor producing diacetoxybutene characterized in that in yieldingdiacetoxybutene by feeding butadiene, acetic acid, and oxygen in thepresence of a solid catalyst containing palladium, an oxygen-containinggas containing 7 mol % or more oxygen is fed as fine bubbles to areaction zone containing the solid catalyst.

The second essential point of the invention resides in a method ofcontact catalytic reaction comprising introducing a gas and a liquidinto a lower part of a reaction zone comprising a liquid phase and acatalyst-packed bed held therein, passing the gas and liquid through thecatalyst-packed bed as a flow of a gas/liquid mixed phase comprising theliquid and bubbles of the gas finely dispersed therein, and causing agas and a liquid containing a reaction product to flow out of an upperpart of the reaction zone, characterized in that thehorizontal-direction movement of the gas/liquid mixed phase flow aroundthe lower side of the catalyst-packed bed is controlled by disposing,under the catalyst-packed bed, flow control plates projecting downwardfrom the lower side of the bed.

The third essential point of the invention resides in a method ofcontact catalytic reaction comprising introducing a gas and a liquidinto a lower part of a reaction zone comprising a liquid phase and acatalyst-packed bed held therein, passing the gas and liquid through thecatalyst-packed bed, and causing a gas and a liquid containing areaction product to flow out of an upper part of the reaction zone,characterized in that the catalyst-packed bed is formed so as to have aporosity of from 0.30 to 0.41.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1, FIG. 2, and FIG. 4 respectively illustrate flow sheet examplesfor practicing the invention, and FIG. 3 illustrates a flow sheetexample for a conventional technique. FIG. 5 is a view diagrammaticallyillustrating an example of flow control plates.

BEST MODE FOR CARRYING OUT THE INVENTION

First, an explanation will be made mainly on the first essential pointof the invention.

The first essential point of the invention resides in a process forproducing diacetoxybutene characterized in that in yieldingdiacetoxybutene by feeding butadiene, acetic acid, and oxygen in thepresence of a solid catalyst containing palladium, an oxygen-containinggas containing 7 mol % or more oxygen is fed as fine bubbles to areaction zone containing the solid catalyst.

In the invention, a zone in which the reaction product is yielded, e.g.,a zone wherein a solid catalyst is present in a liquid phase comprisingbutadiene and acetic acid, is referred to as a reaction zone. Namely,the reaction zone as a whole is occupied by a liquid phase. Anoxygen-containing gas is introduced into the liquid phase of thereaction zone so as to form fine bubbles, whereby diacetoxybutene isyielded.

The introduction of an oxygen-containing gas as fine bubbles into theliquid phase accelerates oxygen dissolution in the liquid phase. This isbecause fine bubbles have an exceedingly large surface area per unitvolume and because the oxygen contained in the gaseous phase dissolvesin the liquid phase through the interface between the two phases. Theoxygen present in the oxygen-containing gas hence dissolves rapidly inthe surrounding liquid phase. The diameter of the bubbles is generally10 mm or smaller, preferably 5 mm or smaller, more preferably 3 mm orsmaller, especially preferably 1 mm or smaller.

As a result of the acceleration of oxygen dissolution in the liquidphase, the oxygen concentration in the bubbles decrease rapidly and theformation of an explosive composition under reaction conditions is aptto be avoidable. Even when violent combustion occurs within part of thebubbles, this does not lead to an explosion such as in chain reactionsbecause the energy of the combustion is low.

Furthermore, as long as the residence time of the bubbles in thereaction zone is adequate, the oxygen concentration in the bubblesdecreases considerably and becomes sufficiently lower than the lowerexplosion composition limit before the bubbles leave the reaction zone.

Consequently, the introduction of an oxygen-containing gas as finebubbles into the liquid phase makes it possible to use anoxygen-containing gas in which oxygen is present in a highconcentration. The oxygen concentration of the oxygen-containing gas isgenerally 7 mol % or higher, preferably 12 mol % or higher. Examples ofsuch an oxygen-containing gas include air diluted with a gas notparticipating in the reaction, such as nitrogen, and further includeair, oxygen-enriched air, diluted oxygen gas, oxygen gas, and the like.

In a preferred embodiment of the invention, an oxygen-containing gashaving such a high oxygen concentration as to form an explosivecomposition under the conditions employed in the reaction zone is fed tothe reaction zone and the residence time of the bubbles in the reactionzone is regulated so that the bubbles at the outlet from the reactionzone has an oxygen concentration lower than the lower explosioncomposition limit.

Incidentally, when the reaction is conducted under ordinary conditions,i.e., under such conditions that the pressure is from 3 to 8 MPa, thetemperature is from 60 to 120° C., and the liquid phase is mostly,occupied by acetic acid, then the lower explosion composition limit canbe estimated at a safety-side value using the following equation (1) or(2):Y=−0.1{(x/0.098)−1}+12   (1)Y=−0.01{(x/0.098)−1}+6.6   (2)(wherein Y represents the lower limit of oxygen concentration (mol %)necessary for forming an explosive composition, and x represents thepressure (MPa) of the reaction zone; equation (1) is used when x≦6 MPa,and equation (2) is used when 6<x≦8 MPa). This estimated value may beused to determine the concentration of the oxygen-containing gas to befed to the reaction zone and the concentration of the oxygen-containinggas to be caused to flow out of the reaction zone.

Techniques for introducing an oxygen-containing gas as fine bubbles intothe liquid phase are not particularly limited. However, in the case ofdirectly introducing an oxygen-containing gas into the reaction zone, itis preferred to feed the gas through two or more parts to the reactionzone with a sparger or the like so as to form fine bubbles.

It is also possible to disperse beforehand an oxygen-containing gas soas to form fine bubbles into the liquid phase to be fed to the reactionzone. For example, a preferred method is as follows. Aliquid-circulating path for withdrawing the reaction liquid from thereaction zone and supplying the liquid to a lower part of the reactionzone is formed. Mixing devices are disposed in this circulating path intwo-stage arrangement. An oxygen-containing gas is supplied to theformer mixing device to disperse the gas as fine bubbles into thereaction liquid flowing through the circulating path. Subsequently,butadiene is supplied to the latter mixing device to mix the butadienewith the reaction liquid containing the oxygen-containing gas dispersedtherein as fine bubbles.

The method described above in which an oxygen-containing gas andbutadiene are mixed with the reaction liquid flowing through thecirculating path and the resultant mixture is fed to the reaction zoneis effective in preventing the reaction zone from having localunevenness of oxygen or butadiene concentration and in thereby enablingthe reaction to proceed smoothly.

Examples of methods for mixing an oxygen-containing gas and butadienewith the reaction to liquid flowing through the circulating pathinclude: a method in which an oxygen-containing gas and butadiene aresimultaneously mixed; a method in which butadiene is mixed and anoxygen-containing gas is then mixed; a method in which anoxygen-containing gas is mixed first and butadiene is then mixed; andthe like. However, the method in which an oxygen-containing gas is mixedfirst and butadiene is then mixed is preferred in that it can form finebubbles without fail.

Any desired mixing devices may be disposed in the circulating path aslong as the desired mixing effect is attained therewith. However, staticmixers are preferred. As is well known, a static mixer is an in-linemixing device which is to be disposed in a piping and has no mechanicaldriving parts and in which a member called an element has been disposedinside in place of a mechanical part. When fluids such as liquids orgases pass through a static mixer, they undergo separation and inversiondue to the element and mixing/dispersion thus proceeds. By the use of astatic mixer, an oxygen-containing gas can be dispersed as fine bubbleshaving a diameter of preferably 3 mm or smaller, especially preferably 1mm or smaller, into the reaction liquid passing through the circulatingpath. This effect is enhanced by regulating the ratio of the volume ofthe gas to that of the liquid to from 0.05 to 1.0.

In the case where a gas/liquid mixed phase flow comprising a reactionliquid and an oxygen containing gas finely dispersed therein is fed to alower part of the reaction zone, it is preferred to feed the mixed phasethrough many nozzles disposed throughout the reaction zone so that themixed phase is evenly fed to the whole reaction zone. The openingdiameter of the nozzles and the number of the nozzles may be suitablydetermined according to the sectional area of the reaction zone intowhich the gas/liquid mixed phase flow is discharged from the nozzles.

The flow rate of the gas/liquid mixed phase discharged from the nozzlesis usually 5 m/sec or lower, preferably from 0.5 to 3 m/sec. As long asthe flow rate is within this range, the gas/liquid mixed phase flow canbe diffused into the whole reaction zone with great ease, withoutraising difficulties in apparatus modification by enlarging thesectional area of all nozzle openings.

It is preferred to dispose a collision plate (baffle plate) above eachnozzle so that the gas/liquid mixed phase flow discharged from thenozzle collides against it and thereby disperse in cross directions. Thesize of the collision plate is generally from 1 to 9 times the sectionalarea of the nozzle opening. Namely, in the case of an ordinary nozzlewith a circular section, a disk of a size about from 1 to 3 times, thediameter of the nozzle may be disposed concentrically above the nozzle.

Although the position in which the collision plate is to be disposed issuitably regulated according to the sectional area of the nozzle openingand the rate of discharge, it is generally preferably at from 5 to 30 cmabove the nozzle outlet. Especially when the position of the collisionplate is within this range, the movement of the gas/liquid mixed phaseflow discharged is not inhibited and the cross-direction dispersion ofthe gas/liquid mixed flow is sufficient. In general, the larger thesectional area of the opening of the nozzle used, the more theregulation of the size and position of the collision plate is important.For disposing nozzles and collision plates as described above, it isgenerally preferred to pack the solid catalyst so as to form acatalyst-packed bed. In this case, the reaction, zone is in thecatalyst-paced bed. Usually, the catalyst-packed bed has been fixed witha catalyst-supporting material.

After the gas/liquid mixed phase flow comprising a reaction liquid andan oxygen-containing as finely dispersed therein has ascended to aroundthe lower side of the catalyst-packed bed, the gas/liquid mixed phaseflow tends to partly flow in horizontal directions along the lower sideof the catalyst-packed bed. Consequently, flow control plates projectingdownward from the lower side of the catalyst-packed bed are disposed soas to prevent the gas/liquid mixed phase flow from moving in horizontaldirections beyond these flow control plates. This is preferred for theefficient production of diacetoxybutene. Namely, the lower side of thebed is partitioned into many sections with the flow control plates sothat the gas/liquid mixed phase flow which has flowed into each sectionenters the catalyst-packed bed through this section.

The flow control plates are preferably disposed so that the upper end ofthe plates is in contact with the lower side of the catalyst-packed bedor is located under the lower side of the catalyst-packed bed through acatalyst-supporting material. In the case where the flow control platesare disposed so that the upper end thereof is apart from the lower sideof the catalyst-packed bed, the distance between the upper end of theflow control plates and the lower side of the catalyst-packed bed isgenerally preferably 20 mm or shorter from the standpoint of preventingthe gas/liquid mixed phase flow from moving in horizontal directions.The catalyst-supporting material may have been united with the flowcontrol plates.

Furthermore, the height of the flow control plates, i.e., the lengthover which the plates project downward, is generally 30 mm or more,preferably 100 mm or more. Although there is no particular upper limiton the height of the flow control plates, the height thereof isgenerally up to 30 cm. This range is especially preferred from thestandpoint of enabling the gas/liquid mixed phase flow to evenly flowinto the sections formed with the flow control plates.

Although the number of sections to be formed with the flow controlplates depends on the cross-sectional area of the catalyst-packed bed,it is preferably 10 or more. The size of each section is preferably 0.25m² or smaller. For example, in the case of square sections, the lengthof each side is preferably 50 cm or smaller. Smaller section sizes areeffective in enabling the gas/liquid mixed phase flow to evenly enterthe catalyst-packed bed even when the bed has large local differences inflow resistance. There is no particular lower limit on the size of eachsection. However, when the catalyst-packed bed is an industrial-scaleone, the size of each section is preferably 9×10⁻⁴ m² or larger. Forexample, in square sections, the length of each side is preferably 3 cmor larger. FIG. 5 diagrammatically shows an example of the flow controlplates.

The height-direction distance between the lower end of the flow controlplates and the inlet for gas introduction into the reaction zone ispreferably 20 cm or longer, more preferably 50 cm or longer, although itdepends on methods of liquid and gas introduction into the reactionzone, the superficial velocities thereof, etc. The upper limit of thatdistance is preferably 3 m or shorter. By regulating that distance so asto be within this range, the gas/liquid mixed phase flow entering eachsection can be easily made even.

The effect of the flow control plates is significant in largecatalyst-packed beds having a sectional area of 1 m² or larger,especially 3 m² or larger.

The catalyst to be used in the invention is one comprising a supportand, having provided thereon, palladium and a promoter ingredient. Asthe support can be used an ordinary one such as, e.g., silica, alumina,silica-alumina, titania, or activated carbon. Examples of the promoteringredient include tellurium, bismuth, antimony, selenium, copper, andthe like. The palladium content of the supported palladium catalyst ispreferably from 0.1 to 20% by weight. The content of the promoteringredient, e.g., bismuth or selenium, therein is preferably from 0.01to 30% by weight.

The catalyst may be in a spherical, solid cylinder, or hollow cylinderform or in the form of crushed particles, etc. However, a spherical ornearly spherical form is preferred. The size of the catalyst ispreferably about from 1 to 6 mm. When the catalyst size is larger than 1mm, the resistance of the passing of the gas/liquid mixed phase flowthrough the catalyst-packed bed is lower. On the other hand, catalystsizes smaller than 6 mm result in a larger area of reaction sites perunit volume. The size of a catalyst is the arithmetic average of thelongest diameter of a projected figure and the length of the longest oneof the diameters perpendicular to that longest diameter. The catalyst ispreferably packed so as to result in a packing density of 0.35 g/ml orhigher. The packing density is determined by dividing the weight of thecatalyst packed in the catalyst-packed bed by the volume of thecatalyst-packed bed.

In the invention, a fixed bed is used as the catalyst-packed bed.

In the invention, the catalyst-packed bed is desirably formed so as toresult in a porosity of generally from 0.30 to 0.41, preferably from0.33 to 0.40. When the porosity is lower than 0.41, the catalystparticles are inhibited from readily flowing, whereby the friction amongthe catalyst particles is reduced accordingly and catalyst deteriorationis reduced. When the porosity is higher than 0.30, catalyst packing iseasier and the power cost can be prevented from increasing because theresistance of the passing of the gas/liquid mixed phase flow through thecatalyst-packed bed is lower.

Apparatus for packing the catalyst are not particularly limited. Forexample, use may be made of those disclosed in U.S. Pat. Nos. 3,804,273and 4,433,707, etc.

The porosity of a catalyst-packed bed is calculated using the followingequation:Porosity of catalyst-packed bed=1−Ax(1/B+C)(wherein A indicates the packing density g/cm³) of the catalyst; Bindicates the true density (g/cm³) of the catalyst; and C indicates thepore volume (ml/g) of the catalyst).The true density of the catalyst can be calculated from the wt % of eachcomponent in the catalyst and the density thereof. The pore volume ofthe catalyst can be determined by the method of mercury penetration.

It is preferred in the invention that a catalyst-packed bed be formed soas to have a porosity of from 0.30 to 0.41 and a liquid and a gas beintroduced into a lower part of the catalyst-packed bed and passedtherethrough as an upward flow. The superficial velocity of each feedmaterial is preferably in the range of from 0.05 to 10 cm/sec. In thecase of producing diacetoxybutene from butadiene, acetic acid, andoxygen, the superficial velocity of an oxygen-containing gas ispreferably in the range of from 0.05 to 10 cm/sec, and the superficialvelocity of a liquid comprising butadiene and acetic acid is preferablyin the range of from 1 to 20 times the superficial velocity of theoxygen-containing gas.

In the invention, the reaction can be conducted in an ordinary way.Usually, the reaction is performed at from 60 to 120° C. and from 3 to 8MPa. Although the reaction may be conducted under conditions outsidethat range according to need, it is preferred to employ that range inview of reaction rate, side reactions, apparatus cost, etc. Since thisreaction is an exothermic reaction, a large amount of acetic acidserving also as a solvent is cause to be present in the reaction zone inorder to facilitate temperature regulation in the reaction zone.Furthermore, a liquid-circulating path may be formed for circulating thereaction liquid, and this circulating path may be provided with acooling device. Preferably, the cooling device is disposed before themixing device so that an oxygen-containing gas is mixed with anddispersed into the reaction liquid which has been cooled. It is alsopreferred that the acetic acid to be fed to the reaction zone besupplied, before the cooling device, to the reaction liquid which isflowing through the circulating path. In a preferred mode of reactiontemperature regulation, the reaction products which are flowing out ofthe reaction zone are partly withdrawn from the system and subjected toa post-treatment step in which the diacetoxybutene yielded is recovered,and the remainder is cooled and circulated to the reaction zone.

Furthermore, the acetic acid and butadiene to be freshly fed arepreferably mixed with the circulating flow before being fed to thereaction zone. The ratio (volume ratio) of the gaseous phase to theliquid phase to be introduced into the reaction zone, i.e., the sum ofthe circulating flow and the acetic acid and butadiene to be freshlyfed, is preferably from 0.05 to 1.0. Although the acetic acid,butadiene, and oxygen-containing gas to be fed to the reaction zone areusually introduced as cocurrent flows into the reaction zone, they maybe introduced as countercurrent flows into the reaction zone accordingto need.

An example of flow sheets for the production of diacetoxybutene by theprocess of the invention is shown in FIG. 1. In the figure, numeral 101denotes a reactor, in which a solid catalyst containing palladium hasbeen packed so as to form a fixed bed. For the purpose of avoidingdrift, the catalyst bed is preferably formed in two or more layersperpendicular to the flow. Numeral 102 denotes a feed pipe for anoxygen-containing gas. The oxygen-containing gas fed is discharged asfine bubbles with a sparger 103 into a lower part of the reactor. Thegaseous phase and liquid phase flowing out of the reactor are introducedthrough a piping 104 into a gas/liquid separator 105. The gaseous phasein the gas/liquid separator is discharged from the system through apiping 106. The liquid phase is discharged through a circulating piping107 and introduced into a lower part of the reactor through acirculating pump 108, cooler 109, and piping 110. The liquid phasecontaining diacetoxybutene in an amount corresponding to thediacetoxybutene yielded in the reactor is withdrawn somewhere in thecirculating piping 107 through a piping 111 and is sent to apost-treatment step for recovering diacetoxybutene. Somewhere in thepiping 110, butadiene and acetic acid as feed materials are suppliedthrough feed pipes 112 and 113, respectively. The butadiene and aceticacid may be supplied to the piping 110 after the cooler 109. Of theliquid phase withdrawn from the gas/liquid separator, the part which isdischarged from the system through the piping 111 usually accounts forfrom 10 to 30% of the liquid phase, and the remainder, which accountsfor from 90 to 70%, is circulated to the reaction zone. Namely, a largeamount of the liquid phase is circulated through the reactor 101,gas/liquid separator 105, and cooler 109 and this circulating flow isused to regulate the temperature of the reactor 101 to be constant.

Another example of flow sheets for the production of diacetoxybutene bythe process of the invention is shown in FIG. 2. In the figure, numeral201 denotes a reactor, in which a solid catalyst containing palladiumhas been packed. The catalyst usually constitutes a fixed bed, and hasbeen packed in two or more separate layers perpendicular to thedirection of the flow for the purpose of avoiding drift. As the catalystmay be used an ordinary supported palladium catalyst. Namely, use may bemade of one comprising a support such as silica, alumina, or activatedcarbon and, having provided thereon, palladium and a promoter such asbismuth, selenium, antimony, tellurium, copper, or the like. Thepalladium content of the supported palladium catalyst is preferably from0.1 to 20% by weight, and the content of the promoter ingredient, e.g.,bismuth or selenium, is preferably from 0.1 to 30% by weight.

Numeral 202 denotes a gas/liquid separator, into which the effluent fromthe reactor 201 flows through a piping 207. The gaseous phase isdischarged from the system through the piping 208, and the liquid phaseis withdrawn through a circulating piping 209. The liquid phasecontaining diacetoxybutene in an amount corresponding to thediacetoxybutene yielded by the reaction is withdrawn from thecirculating piping 209 through a piping 210 and sent to a post-treatmentstep for recovering diacetoxybutene. Of the liquid phase withdrawn fromthe gas/liquid separator, the part which is discharged from the systemthrough the piping 210 usually accounts for from 10 to 30% of the liquidphase, and the remainder, which accounts for from 90 to 70%, is suppliedto a lower part of the reactor 201 through a pump 203, cooler 204,former mixing device 205, and latter mixing device 206. Namely, a largeamount of a reaction liquid is flowing through the circulating piping209. Acetic acid is supplied to this reaction liquid through a piping211. Subsequently, an oxygen-containing gas is supplied through a piping212, and the reaction liquid is supplied together with theoxygen-containing gas to former mixing device 205, where the gas isdispersed as fine bubbles into the reaction liquid. Butadiene issupplied to the resultant gas/liquid mixed phase flow through a piping213. The butadiene is added to the reaction liquid, and these aresupplied to the latter mixing device 206, evenly mixed, and fed to thereactor 201.

According to the invention, a high-concentration oxygen-containing gascan be used and oxygen can be rapidly dissolved in the liquid phase inthe reaction zone. Because of this, the amount of butadiene which reactsper unit catalyst amount and unit time can be increased as compared withconventional techniques.

Next, an explanation will be made on the second essential point of theinvention.

The second essential point of the invention resides in a method ofcontact catalytic reaction comprising introducing a gas and a liquidinto a lower part of a reaction zone comprising a liquid phase and acatalyst-packed bed held therein, passing the gas and liquid through thecatalyst-packed bed as a flow of a gas/liquid mixed phase comprising theliquid and bubbles of the gas finely dispersed therein, and causing agas and a liquid containing a reaction product to flow out of an upperpart of the reaction zone, characterized in that thehorizontal-direction movement of the gas/liquid mixed phase flow aroundthe lower side of the catalyst-packed bed is controlled by disposing,under the catalyst-packed bed, flow control plates projecting downwardfrom the lower side of the bed.

In this invention, the flow control plates are as described above andcan be applied to conventional gas/liquid mixed phase flows. They areapplicable also to various reactions in which a gaseous startingmaterial is reacted with a liquid starting material in the presence of asolid catalyst. Examples of such reactions include catalytichydrogenation reactions such as the production of γ-butyrolactone or1,4-butanediol by maleic anhydride hydrogenation, production ofcyclohexane by benzene hydrogenation, production of alcohols by thehydrogenation of carboxylic acid esters, production of 1,6-hexanediol byadipic acid hydrogenation, and purification of crude terephthalic acidby hydrogenation. Preferred applications among these are the reactionsusing a supported noble-metal catalyst, such as, e.g., the production of1,6-hexanediol by adipic acid hydrogenation or purification of crudeterephthalic acid by hydrogenation.

Specifically, the flow control plates described above are effective inintroducing a gas/liquid mixed phase flow into a reaction zone as in thecase of, for example, mixing an oxygen-containing gas with a liquid feedmaterial or reaction liquid and feeding the mixture to a reaction zoneas explained with regard to the first essential point of the invention.

An explanation will then be given on the third essential point of theinvention.

The third essential point of the invention resides in a method ofcontact catalytic reaction comprising introducing a gas and a liquidinto a lower part of a reaction zone comprising a liquid phase and acatalyst-packed bed held therein, passing the gas and liquid through thecatalyst-packed bed, and causing a gas and a liquid containing areaction product to flow out of an upper part of the reaction zone,characterized in that the catalyst-paced bed is formed so as to have aporosity of from 0.30 to 0.41.

In this invention, the porosity of the catalyst-packed bed is as shownabove. The porosity range of from 0.30 to 0.41 is applicable to variousreactions heretofore in use in which a gaseous starting material isreacted with a liquid starting material in the presence of a solidcatalyst. Examples of such reactions include catalytic hydrogenationreactions such as the production of γ-butyrolactone or 1,4-butanediol bymaleic anhydride hydrogenation, production of cyclohexane by benzenehydrogenation, production of alcohols by the hydrogenation of carboxylicacid esters, production of 1,6-hexanediol by adipic acid hydrogenation,and purification of crude terephthalic acid by hydrogenation. Preferredapplications among these are the reactions using the supportednoble-metal catalyst, such as, e.g., the production of 1,6-hexanediol byadipic acid hydrogenation or purification of crude terephthalic acid byhydrogenation.

Specifically, regulating the porosity of the catalyst-packed bed to avalue of from 0.30 to 0.41 as described above is effective inintroducing a gas/liquid mixed phase flow into a reaction zone as in thecase of, for example, mixing an oxygen-containing gas with a liquid feedmaterial or reaction liquid and feeding the mixture to a reaction zoneas explained with regard to the first essential point of the invention.

The invention will be explained below in more detail by reference toExamples, but the invention should not be construed as being limited tothese Examples.

EXAMPLE 1

According to the flow sheet shown in FIG. 1, diacetoxybutene wasproduced from butadiene and acetic acid. A 5 wt % Pd-1.5 wt % Te/SiO₂catalyst prepared by allowing silica to support palladium and telluriumwas packed into a reactor so as to form a fixed bed. A circulatingliquid containing freshly supplied butadiene and acetic acid was fed toa lower part of the reactor at 77° C. and 6 MPa, and air was fed througha sparger having a hole diameter of 3 mm at a flow rate of 20 m/sec soas to form fine bubbles. The amounts of the butadiene and acetic acidfreshly fed were 0.223 kg/hr and 3.235 kg/hr, respectively, per kg ofthe catalyst. The amount of the air fed was 0.454 kg/hr per kg of thecatalyst, and the amount of the circulating flow withdrawn from thegas/liquid separator and introduced into the reactor was 14.306 kg/hrper kg of the catalyst. The amount of the butadiene contained in thiscirculating flow and introduced into the reactor was 0.055 kg/hr per kgof the catalyst. The reaction was thus conducted continuously. As aresult, the rate of reaction of the butadiene was 0.205 kg/hr per kg ofthe catalyst. The air bubbles fed through the sparger had a diameter offrom 3 to 4 mm.

EXAMPLE 2

A reaction for yielding diacetoxybutene from butadiene and acetic acidwas conducted in completely the same manner as in Example 1, except thatoxygen-enriched air having an oxygen concentration of 25.0 mol % wasused as an oxygen-containing gas. The rate of reaction of the butadienewas 0.213 kg/hr per kg of the catalyst.

COMPARATIVE EXAMPLE 1

Diacetoxybutene was yielded from butadiene and acetic acid by the gascirculation method shown in FIG. 3. In the figure, 301 denotes a firstreactor packed with the same catalyst as used in Example 1. Butadieneand acetic acid to be freshly fed were fed to an upper part of thereactor 301 through pipings 302 and 303 At 77° C. and 6 MPa. Air was fedto the upper part of the reactor 301 through a piping 304 and agas-circulating piping 305. The effluent from the reactor 301 was cooledto 77° C. with a cooler 306 and then fed to a second reactor 307 packedwith the same catalyst as in the first reactor. The first reactor 301and second reactor 307 each was of the type in which a liquid phaseflowed down along the catalyst held in a gaseous atmosphere. Theeffluent from the second reactor was introduced into a gas/liquidseparator 309 through a piping 308. The liquid phase was withdrawn fromthe system through a piping 310, and the gaseous phase was circulated tothe reactor 301 through a piping 305. The piping 305 had a cooler 311and compressor 312 disposed therein, and part of the circulating gas waswithdrawn from the system through a piping 313. The amounts of thebutadiene and acetic acid freshly fed were 0.187 kg/hr and 8.111 kg/hr,respectively, per kg of the catalyst. The amount of the air fed was0.380 kg/hr per kg of the catalyst, and the amount of the circulatinggas fed from the gas/liquid separator through a piping was 2.708 kg/hrper kg of the catalyst. The amount of the butadiene contained in thiscirculating gas and introduced into the reactors was 0.046 kg/hr per kgof the catalyst. The circulating gas which had been mixed with the airsupplied through the piping 304 had an oxygen concentration of 5.6 mol%. The rate of reaction of the butadiene was 0.186 kg/hr per kg of thecatalyst.

EXAMPLE 3

According to the flow sheet shown in FIG. 2, diacetoxybutene wasproduced from butadiene and acetic acid. A 5 wt % Pd-1.5 wt % Te/SiO₂catalyst prepared by allowing silica to support palladium and telluriumwas packed into a reactor so as to form a fixed bed. A static mixer wasemployed as each of the former and latter mixing devices disposed in thecirculating piping. Air was used as an oxygen-containing gas. The amountof the reaction liquid fed to a lower part of the reactor through thecirculating piping was 14.306 kg/hr per kg of the catalyst, and theamounts of the acetic acid, air, and butadiene mixed with the reactionliquid were 3.235 kg/hr, 0.454 kg/hr, and 0.223 kg/hr, respectively, perkg of the catalyst. The amount of the butadiene contained in thereaction liquid and introduced into the reactor was 0.055 kg/hr per kgof the catalyst. The gas/liquid mixed phase flow was fed through thecirculating piping to the reactor with sixteen circular nozzles at aflow rate of 2 m/sec. A disk having a diameter 2.3 times the diameter ofthe nozzles was horizontally disposed at 20 cm above each nozzleconcentrically with the nozzle. The gas/liquid mixed phase flow fromeach nozzle was caused to collide against the disk and disperse. Thesize of the bubbles of the gas/liquid mixed phase flow was 1 mm orsmaller. This gas/liquid mixed phase flow was introduced into thereactor at 77° C. and 6 MPa. The reaction was continuously conductedunder these conditions. As a result, the rate of reaction of thebutadiene was 0.222 kg/hr per kg of the catalyst.

EXAMPLE 4

A 5 wt % Pd-1.5 wt % Te/SiO₂ catalyst prepared by allowing a silicasupport (product of Fuji Silysia Ltd.; CARiACT-17; spherical productwith a diameter of 2.4-4 mm) to support palladium and tellurium throughimpregnation was introduced in an amount of 1,410 g into a cylindricalreactor having an inner diameter of 49.5 mm and a length of 2,000 mmthrough the upper opening thereof. The catalyst was densely packed byvibrating the reactor with a hammer. The packing density of the catalystwas 0.47 g/ml. The pore volume of the catalyst as measured by the methodof mercury penetration was 0.87 ml/g, and the true density of thecatalyst calculated from the components was 2.32 g/cm³. Consequently,the porosity of the catalyst-packed bed was 0.39. A metal gauze was laidon the catalyst-packed bed, and zirconia spheres having a diameter of 10mm were packed thereon so as to form a zirconia sphere layer having aheight of 180 mm.

The reactor was maintained at 6 MPa, and 70° C. acetic acid containingbutadiene and 70° C. nitrogen gas containing oxygen were continuouslyintroduced into a lower part of the reactor at superficial velocities of1.8 cm/sec and 1.5 cm/sec, respectively, and passed through thecatalyst-packed bed upward. The nitrogen gas containing oxygen wasintroduced with a sparger so as to form fine bubbles. The liquid and gasintroduction was thus continued over 2,700 hours to conduct a reactionfor yielding diacetoxybutene. Thereafter, the catalyst was withdrawnthrough the upper part of the reactor and examined for palladiumcontent. As a result, the palladium content had not decreased at all.Furthermore, the surface of the catalyst withdrawn was examined with anoptical microscope (magnification, 50 diameters). As a result, almost nomars formed by friction were observed.

EXAMPLE 5

The same reactor as used in Example 4 was filled with water. Thisreactor was packed with 1,410 g of the same 5.2 wt % Pd-1.5 wt % Te/SiO₂catalyst as used in Example 4, which had been prepared by allowing asilica support to support palladium and tellurium, to form acatalyst-packed bed. The catalyst had a packing density of 0.44 g/ml anda porosity of 0.43. A metal gauze was laid on the catalyst-packed bed,and zirconia spheres having a diameter of 10 mm were packed thereon soas to form a zirconia sphere layer having a height of 180 mm.

Acetic acid containing butadiene and nitrogen gas containing oxygen werecontinuously introduced into the reactor over 2,700 hours in completelythe same manner as in Example 4 to conduct a reaction for yieldingdiacetoxybutene. Subsequently, the catalyst was withdrawn through theupper part of the reactor and examined for palladium content. As aresult, the palladium content was found to be 4.8% by weight, i.e., ithad decreased to 92.3% of the initial content. Furthermore, the surfaceof the catalyst withdrawn was examined with an optical microscope. As aresult, many mars formed by friction were observed.

REFERENCE EXAMPLE 1 Example of Catalytic Activity Test

A reaction tube having an inner diameter of about 12 mm (sectional area,1.005 cm²) was packed with 4 g of a catalyst and maintained at 6 MPa and80° C. Butadiene, acetic acid, and nitrogen gas containing 6 mol %oxygen were continuously introduced upward into the reaction tube fromits bottom at rates of 0.15 mol/hr, 2.5 mol/hr, and 100 NL/hr,respectively, to yield diacetoxybutene. A reaction liquid obtained inthe period from 4 hours after initiation of the reaction to 5 hoursafter the initiation and a reaction liquid obtained in the period from 6hours after the initiation to 7 hours after the initiation were analyzedby gas chromatography. The rate of consumption (mmol/hr) of thebutadiene per kg of the catalyst was calculated from the average ofthose found values and taken as catalytic activity. The results obtainedare shown in Table 1. TABLE 1 Catalyst Catalytic activity A 8810 B 8760C 8640 D 7700

In the table, A is the same catalyst as used in Example 4; B is thecatalyst withdrawn from the catalyst-packed bed after 2,700 hours inExample 4; C is the same catalyst as used in Example 5; and D is thecatalyst withdrawn from the catalyst-packed bed after 2,700 hours inExample 5.

The catalyst used in Example 4 had suffered almost no frictional damageand, hence, underwent a decrease in catalytic activity as small as 0.6%even through the 2,700-hour reaction. In contrast, in the catalyst usedin Example 5, the surface palladium had partly shed off due tofrictional damage. Because of this, the catalyst used in Example 5underwent a decrease in catalytic activity of 10.9% through the2,700-hour reaction.

EXAMPLE 6

According to the flow sheet shown in FIG. 4, butadiene, acetic acid, andan oxygen-containing gas are reacted to produce diacetoxybutene. In thefigure, 401 denotes a reactor. The reactor has a catalyst-packed bed 403on a catalyst-supporting material 402 made of a metal gauze. Thecatalyst is a 5.0 wt % Pd-1.5 wt % Te/SiO₂ catalyst prepared by allowinga silica support to support palladium and tellurium throughimpregnation. Partition plates (flow control plates) having a height of20 cm are arranged at right angles on the lower side of thecatalyst-supporting material so as to partition the lower side into manysquares of 20 cm×20 cm. Numeral 404 denotes a sparger for theoxygen-containing gas. The distance between the gas outlets of thesparger and the lower end of the partition plates is 120 cm. Agas/liquid mixed phase flow from the reactor is introduced into agas/liquid separator 406 through a piping 405. The gaseous phase iswithdrawn from the system through a piping 407. The liquid-phase iscirculated to a lower part of the reactor 401 through a circulatingpiping 408 having a circulating pump 409 and cooler 410 disposedtherein. A reaction liquid containing diacetoxybutene in an amountcorresponding to the diacetoxybutene yielded by the reaction iswithdrawn somewhere in the circulating piping through a piping 411 andsent to a product-treating system. Butadiene and acetic acid weresupplied to the circulating piping through a piping 412 and a piping413, respectively.

The reactor is maintained at 6 MPa, and a circulating reaction liquid,butadiene, acetic acid, and air are continuously fed thereto tocontinuously yield diacetoxybutene. The temperature of the circulatingreaction liquid being fed is 77° C. The amounts of the circulatingreaction liquid, butadiene, acetic acid, and air fed per kg of thecatalyst are 14.3 kg/hr, 0.223 kg/hr, 3.24 kg/hr, and 0.454 kg/hr,respectively. The amount of butadiene in the circulating reaction liquidis 0.055 kg/hr per kg of the catalyst. The feed materials were reactedunder these conditions. As a result, the rate of reaction of thebutadiene was 0.211 kg/hr per kg of the catalyst.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

This application is based on a Japanese patent application filed on Oct.13, 2000 (Patent Application No. 2000-313366), Japanese patentapplication filed on October 30, 2000 (Patent Application No.2000-330550), Japanese patent application filed on Nov. 1, 2000 (PatentApplication No. 2000-334137), and Japanese patent application filed onNov. 20, 2000 (Patent Application No. 2000-352446), the contents thereofbeing hereby incorporated by reference.

Industrial Applicability

The invention relates to a process for producing diacetoxybutene, whichis an important compound as an intermediate for producing 1,4-butanediolor tetrahydrofuran, by reacting butadiene, acetic acid, and oxygen, andaccording to the process it is possible to efficiently react butadieneto produce diacetoxybutene in high yield.

1-15. (canceled)
 16. A method of contact catalytic reaction comprisingintroducing a gas and a liquid into a lower part of a reaction zonecomprising a liquid phase and a catalyst-packed bed held therein,passing the gas and liquid through the catalyst-packed bed as a flow ofa gas/liquid mixed phase comprising the liquid and bubbles of the gasfinely dispersed therein, and causing a gas and a liquid containing areaction product to flow out of an upper part of the reaction zone,wherein the horizontal-direction movement of the gas/liquid mixed phaseflow around the lower side of the catalyst-packed bed is controlled bydisposing, under the catalyst-packed bed, flow control plates projectingdownward from the lower side of the bed.
 17. (canceled)
 18. The processof claim 16, wherein the catalyst-packed bed is filled with a solidcatalyst or solid catalysts.
 19. The process of claim 18, wherein thecatalyst-packed bed is a fixed bed.
 20. The process of claim 16, whereinthe solid catalyst is one provided on the surface of a support selectedfrom the group consisting of silica, alumina, silica-alumina, titania,and activated carbon.
 21. The process of claim 16, wherein theoxygen-containing gas is one containing 12 mol % or more oxygen.
 22. Theprocess of claim 16, wherein the flow control plates are disposed so asto partition the lower side of the catalyst-packed bed into ten or moresections.
 23. The process of claim 16, wherein the flow control platesare disposed so as to partition the lower side of the catalyst-packedbed into sections of 0.25 m² or smaller.
 24. The process of claim 16,wherein the flow control plates project over a length of 30 mm orlonger.
 25. The process of claim 16, wherein the height-directiondistance between an inlet for gas introduction into the reaction zoneand the lower end of the flow control plates is 20 cm or longer.
 26. Theprocess of claim 16, wherein a liquid-circulating path for withdrawing areaction liquid from the reaction zone and supplying the liquid to alower part of the reaction zone is formed and mixing devices aredisposed in this circulating path in two-stage arrangement, and that theformer mixing device is used to feed an oxygen-containing gas anddisperse the gas into the reaction liquid flowing through thecirculating path and butadiene is supplied to the latter mixing deviceand mixed with the reaction liquid.
 27. The process of claim 26, whereinthe mixing devices are static mixers.
 28. The process of claim 16,wherein the catalyst-packed bed has a porosity of from 0.30 to 0.41. 29.The process of claim 28, wherein the catalyst has a particle diameter offrom 1 to 6 mm and the packing density of the catalyst is 0.35 g/ml orhigher.
 30. The process of claim 28, wherein the gas which is beingintroduced into the reaction zone has a superficial velocity of from0.05 to 10 cm/sec.